So, this means that I should use ext-all-dev.js for developement and when I am done with developement then I should use ext-all.js for production?
One more thing here, how do I replace ext-all-dev.js with ext-all.js in all my pages? I saw bootstrap.js but I work on cloud platform so bootstrap.js is going to use ext-all.js in all cases since I am not on localhost. Is there any way I can change bootstrap.js?
ext-all-dev.js logs warnings for common errors. For example, if you forget to include a model in your store config it'll warn you about it. Personally this is the file I'd use for development.
You could alternatively use the individual source files via the loader but personally I prefer ext-all-dev.js.
I can't think of a good reason to ever use ext-all-debug.js. It exists for historical reasons and it wouldn't surprise me if it's dropped from the distribution eventually.
Well, you cannot use ext-all-dev.js in Internet Explorer versions prior to 9 because he doesn't recognize console.log, and in many cases one needs to test for legacy versions of IE. That's were ext-all-debug comes into the picture.